https://discussions.apple.com/thread/250786208

$ defaults read com.apple.systempreferences AttentionPrefBundleIDs
{
    "com.apple.preferences.AppleIDPrefPane" = 1;
}

$ defaults delete com.apple.systempreferences AttentionPrefBundleIDs

or (better)...

https://apple.stackexchange.com/questions/344278/how-can-i-disable-the-red-software-update-notification-bubble-on-the-system-pref

defaults write com.apple.systempreferences AttentionPrefBundleIDs 0